SINGLE CANCER CELL MIGRATION MECHANISMS IN MICROMOLDED 3D COLLAGEN MICROTRACKS Aniqua Rahman Cornell University, 2018 One of the earliest steps of cancer metastasis is cellular migration through the surrounding collagenous stromal extracellular matrix (ECM) after dissemination from the primary tumor. The stroma through which cancer cells navigate is a complex network of fiber architectures. It is known that in vivo, some metastatic cancer cells migrate through pre-existing tracks within the collagenous ECM matrix. A subset of cells termed as “leader” cells create invasion paths (known as “microtracks”) by degrading and remodeling the surrounding matrix using proteolytic enzymes. “Leader” cells first migrate through the stroma leaving “tube-like” microtracks within the ECM of the stroma and other metastatic “follower” cells utilize these pre-existing microtracks as ‘highways’ to escape the primary tumor without any proteolytic activities. Despite numerous studies, the mechanisms modulating cancer cell migration through the stroma and particularly through these microtracks still remain unclear. In general, the process of cellular migration is governed by a balance between the molecular mechanisms regulating migration signaling and the physiological cues posed by the neighboring tumor microenvironment. However, much less is known about how the “follower” cancer cells migrate through these confined in vivo microtracks within the ECM. In this thesis, we utilized microfabrication technique to recreate in vitro collagen microtracks and recapitulate confined non-proteolytic metastatic cell migration to study the behavior of “follower” cells. Our results indicate that cell adhesion and polarization facilitate directional migration in in vitro collagen microtracks. Additionally, cellular focal adhesion dynamics and traction stresses dictate cell migration behavior in confined and partially confined spaces within the microtracks. Moreover, cell compliance and energy requirement impact cell migration choices in confined microtracks. These results help us to define how intracellular signals and extracellular microenvironments direct single cell migration in microtracks. Our findings could potentially lead to a targeted therapeutic approach to inhibit cell migration and ultimately cancer metastasis.